Flat image display

ABSTRACT

A plurality of fixing stands ( 32 ) are attached to the inner face of a rear case ( 10 ), and a back electrode substrate ( 33 ) that functions as a back electrode and an electrode unit ( 11 ) formed by superposing a plurality of electrode plates via insulators are attached to the fixing stands ( 32 ). In this case, only one fixing stand positioned substantially at the center of the back electrode substrate ( 33 ) in the plurality of fixing stands ( 32 ) is fixed to the back electrode substrate ( 33 ), and presser bar plate springs ( 36 ) for pressing the substrate are attached onto the remaining fixing stands to fix the back electrode substrate ( 33 ) by their elasticity. Such an attachment structure enables thermal distortion in fabrication processes and during operation and influences of vibration/impacts from the exterior to be absorbed or eliminated, thus providing a flat-type image display apparatus with high accuracy and high image quality.

TECHNICAL FIELD

The present invention relates to a flat-type image display apparatusused for a television receiver, a computer-terminal display unit, or thelike.

BACKGROUND ART

Recently, the development for reducing the thickness of color imagedisplay apparatus has been carried out actively. Particularly, forexample, Publication of Unexamined Japanese Patent Application(Tokkai-Hei) No. 3-67444 proposes a flat-type image display apparatusemploying a beam scanning method in which the distance from a cathode toan anode is shortened significantly compared with a conventionalcathode-ray tube (CRT) system. In the flat-type image display apparatus,a screen is divided into a plurality of sections vertically. An electronbeam is deflected vertically to display a plurality of lines on eachsection. Further, the screen is also divided into a plurality ofsections horizontally. In each section, phosphors of R, G, and B emitlight sequentially. An amount of electron beams irradiated onto thephosphors of R, G, and B is controlled by the received color picturesignals. Thus, a television picture is displayed as a whole.

In the above-mentioned flat-type image display apparatus, an electrodeunit in which the distance from a cathode to an anode is shortenedsignificantly and linear hot cathodes (hereafter referred to as “linearcathodes”) as electron beam sources are housed in a flat-box type vacuumcase. Electrodes forming the electrode unit are provided with smallholes or slits for deflecting, focusing, and controlling electron beamsemitted from the linear cathodes. The electron beams go through theelectrodes while being controlled by the holes or slits in eachelectrode and accelerated to the anode to cause light emission ofphosphors applied to the anode, thus displaying images.

FIG. 7 is an exploded perspective view showing the internal structure ofa flat-type image display apparatus. In the flat-type image displayapparatus, a back electrode 1, linear cathodes 2 (in the figure, onlyfour linear cathodes are shown) extending horizontally, an electron beamextracting electrode 3, a signal electrode 4, focusing electrodes 5 and6, a horizontal deflection electrode 7, and a vertical deflectionelectrode 8 are arranged sequentially. These sheet-like electrodes 3-8are superposed via insulators and spacers, thus forming an electrodeunit 11. The electron beam extracting electrode 3 is provided withelectron beam extracting holes 12. Electron beams 13 emitted from thelinear cathodes 2 are extracted through the holes 12 so as to form anapparent one electron beam per hole. An extracted electron beam 13 iscontrolled, focused, and deflected by the respective electrodes 4-8 toscan a subsection 14 on the anode screen.

The phosphors of R, G, and B are printed and applied onto screensections, for example, 14-16 in the inner side of a front case 9 that isa flat-box type front glass case. Further, a metal-backed layer isformed on the sections 14-16 to apply high voltage. The electron beamsare accelerated to have high energy and strike the metal-backed layer,thus exciting the phosphors so that the phosphors emit light. Theelectron beam 13 allows the subsection 14 of the screen to emit light todisplay a part of an image. Similarly, other electron beams cause lightemission of all the other subsections, such as the subsection 16, todisplay images. Thus, a desired image is displayed on the whole screen.A rear case 10 and the front case 9 are combined and sealed, and then avacuum is drawn on its inside, thus forming a flat-type image displayapparatus.

FIG. 8 is a perspective view showing the appearance of a sealedflat-type image display apparatus. The front case 9 and the rear case 10are baked to be sealed with low melting point glass. Numeral 17indicates an exhaust pipe for drawing the vacuum inside the case,numeral 18 a high-voltage terminal of the anode, and numeral 19 outgoingterminals for controlling various electrodes forming the electrode unit.By connecting a driving circuit, a signal processing circuit, or thelike to these terminals externally, the flat-type image displayapparatus functions as a television receiver or a display unit.

Internal components constructing the aforementioned flat-type imagedisplay apparatus are exposed to high temperature repeatedly in asealing step in the assembly and fabrication process and duringoperation of the apparatus as an image display apparatus. In otherwords, in the assembly and fabrication process, the apparatus is exposedto a high temperature of about 500° C. both in fixing a plurality offixing stands for attaching various electrodes to the glass rear caseusing low melting point glass and in combining and baking the front caseand the rear case to seal the case using low melting point glass at aperipheral adhering portion of the case. Further, for example, a processof drawing high vacuum inside the glass case after sealing the glasscase is carried out in a heating furnace at about 300-350° C. Thus, theapparatus is heated repeatedly. During the operation of the apparatus asan image display apparatus, a number of linear cathodes stretched in aplane are heated to a high temperature of 600-700° C. for generatingelectron beams. Due to such heat radiation, the various internalelectrodes also are exposed to high temperature.

In order that a proper beam spot scans precisely the screen surface onwhich phosphors have been printed to avoid deviation of beam position onthe screen so as to display vivid images with high precision even if theapparatus is exposed to high temperature in the aforementioned assemblyand fabrication process and during the operation, the apparatus musthave accuracy on a micron level and the accuracy must be maintained.However, generally objects exposed to high temperature repeatedly aresubjected to thermal deformation such as expansion and contractionrepeatedly due to the temperature change. Therefore, in order to allowthe repeated exposure to high temperature and the maintaining of highaccuracy to be compatible, problems of physically incompatibleoccurrences must be solved.

Particularly, while a flat-type image display apparatus has a flatshape, it is necessary to form the apparatus so as to have aglass-plate-like case body with a front case and a rear case, both ofwhich are thick to have a thickness of about 10 mm, to obtain a resistpressure of the outside air by drawing high vacuum inside the case, thuscausing extremely high thermal stress in the above-mentioned assemblyprocess at high temperature.

The problems to be solved in a conventional example will be explainedwith reference to FIGS. 9 and 10 as follows.

FIG. 9 is a plan view showing an example of the arrangement of electrodesupport plates and electrode fixing plates for fixing an electrode unitincluding various electrodes that is attached to the inner face of arear case of a conventional flat-type image displaying apparatus. Inaddition, FIG. 9 schematically shows a state in which thermal expansionand distortion occur in the above-mentioned heating processes.

FIG. 10 is a partial cross-sectional view showing a schematic structureof the flat-type image display apparatus shown in FIG. 9 in which theelectrode unit is attached by fixing the electrode support plates andthe electrode fixing plates that are assembled in a parallel-crossesform to fixing stands.

In FIG. 9, arrows A, B, C, . . . , P show thermal stress lines seen in aplane, and an alternate long and short dash line shows a slightlyexaggerated distortion condition in which a rear case 10, electrodesupport plates 20, and electrode fixing plates 21 have been expanded anddeformed due to the thermal effect as a result of the thermal stress.

Fixing stands 22 for fixing the electrode support plates 20 and the liketo the rear case 10 are displaced according to the expansion andcontraction of the glass-plate like rear case 10, which is not shown inthe figure. The same is applied to the electrode unit to be fixed ontothese electrode support devices.

The expansion caused by heating and the contraction caused by coolingmay not be problems when all the components that are combined inside thecase have the same coefficient of thermal expansion. However, in theconventional example, the case is made of glass, the electrode supportplates 20 and the electrode fixing plates 21 are formed of a 50 Ni—Fematerial, and a plurality of electrode plates forming an electrode unit11 are made of an alloy (for instance, a 36 Ni—Fe alloy) having a lowcoefficient of thermal expansion. Therefore, the difference incoefficient of thermal expansion among those components causes thedifference in distortion due to the thermal deformation. Consequently,cracks and warps occur at weak spots and stress concentration spots,which have been a problem.

FIG. 9 shows that the rear case 10 expands by being heated to theposition shown with the alternate long and short dash line indicatedwith 10′. In this case, fixing stands 22 a˜22 f tend to be displaced inthe same way. An electrode unit (not shown in the figure) is fixed ontothe fixing stands 22 a˜22 d indirectly with fixing screws 23 a-23 drespectively. On the other hand, the electrode plates forming thiselectrode unit serve to control and supply focused electron beams andthe electron beams must accurately strike R, G, and B phosphors thathave been printed on the inner face of a front case 9 minutely.Therefore, when the screen and the electrodes are thermally displaceddifferently, basic performance as an image display apparatus cannot beobtained.

The electrode unit 11 made of a 36 Ni—Fe alloy is fastened and fixed tothe electrode support plates 20 to form one component with screws 24a-24 d for mounting the electrode unit in FIG. 9. The volume ofdeformation of the electrode unit itself is controlled to be small byemploying an alloy that is not thermally deformed much. On the contrary,the electrode support plates 20 and the electrode fixing plates 21 aremade of a 50 Ni—Fe alloy as mentioned above and thus have a coefficientof thermal expansion similar to that of glass. Therefore, the electrodesupport plates 20, the electrode fixing plates 21, and the rear case 10are thermally deformed prior to the change of the electrode unit 11.

In addition, the thermal deformation caused by the difference inaccuracy depending on the dimensional accuracy and assembly accuracy ofthe electrode support plates 20 and the electrode fixing plates 21 alsomust be considered.

In short, the intersection points of the electrode support plates 20 andthe electrode fixing plates 21 that are assembled in a parallel-crossesform are fixed to the electrode unit made of a 36 Ni—Fe alloy using thescrews 24 a-24 d for mounting the electrode unit so as to form onecomponent. Therefore, the electrode support plates 20 and the electrodefixing plates 21 cannot be displaced at their intersection points andthus are displaced at their intermediate points in respective directionsindicated with the arrows A, B, C, and D in a curved manner. Thus, thefixing stands 22 e and 22 f at the intermediate points are affected mostand are the parts where cracks or the like occur easily.

FIG. 10 shows an example of such a state. The difference in displacementmagnitude between the arrow S showing the thermal displacement directionof the electrode fixing plates 21 and the arrow R showing the thermaldisplacement direction of the rear case 10 leads to breakage and causesunwanted occurrence such as cracks 31 and the like in a low meltingpoint glass 30, which has been a problem. In addition, such occurrenceis not uniform, which also has been a problem.

When an external force such as vibration, impact from falling, or thelike is applied, as shown in FIG. 10, the electrode support plates 20serve as points of support since the electrode unit 11 contacts with andis supported by the electrode support plates 20 at both ends of theelectrode unit 11. Thus, the electrode unit 11 resonates at a properfrequency to have the greatest amplitude in the vicinity of the centralportion. In the worst case, the electrode unit 11 and linear cathodes 2come into contact with each other and carbonates that have been appliedto the linear cathodes 2 fall, which has been a problem.

For a plurality of linear cathodes, the electric fields at the centralportion of the case and in the vicinities of the electrode supportplates 20 are not uniform. Therefore, the difference in electron-beamemission capacity among the linear cathodes occurs and thus disturbs theuniformity in an image, which has been a problem.

Furthermore, in spattering a getter that adsorbs gases in a vacuum, thespattered getter adheres onto the linear cathodes and the outgoingterminals, thus causing bad insulation, which has been a problem.

DISCLOSURE OF THE INVENTION

The present invention solves the problems of the above-mentionedconventional flat-type image display apparatus. It is an object of thepresent invention to provide a flat-type image display apparatus thatcan realize and maintain desired assembly accuracy by absorbing thermaldistortion caused by high exposure temperature in fabrication processesand during operation and is not affected much by vibration/impactscaused by external factors.

It also is an object of the present invention to provide a flat-typeimage display apparatus that provides uniform images by canceling thedifference in electron-beam emission capacity among linear cathodes.

Further, it is another object of the present invention to provide aflat-type image display apparatus in which bad insulation caused by theadhesion of spattered getter does not occur.

In order to attain the above-mentioned objects, a flat-type imagedisplay apparatus of the present invention comprises a flat-type screento which phosphors have been applied, a plurality of stretched linearcathodes, an electrode unit including a plurality of sheet-likeelectrode plates, and a back electrode made of a conductive materialthat are arranged in a case formed of a front case and a rear case, andthe case is sealed with its inside being under a vacuum. The flat-typeimage display apparatus of the present invention is characterized by thefollowing structure. A fixing stand is attached to an inner face of therear case; a back electrode substrate that functions as the backelectrode is attached onto the fixing stand; the electrode unit ismounted on the upper face of the back electrode substrate; and theattachment structure of the back electrode substrate and the mountingstructure of the electrode unit have at least one of systems forabsorbing thermal distortion and for preventing vibration/impacts.

A flat-type image display apparatus of the present invention comprises aflat-type screen to which phosphors have been applied, a plurality ofstretched linear cathodes, an electrode unit including a plurality ofsheet-like electrode plates, and a back electrode made of a conductivematerial that are arranged inside a case formed of a front case and arear case, and the case is sealed with its inside being under a vacuum.The flat-type image display apparatus of the present invention ischaracterized by the following structure. A plurality of fixing standsare attached to an inner face of the rear case; a back electrodesubstrate that functions as the back electrode is attached onto thefixing stands; the electrode unit is mounted on the upper face of theback electrode substrate; only one fixing stand positioned substantiallyat the center of the back electrode substrate in the plurality of fixingstands is fixed to the back electrode substrate; and presser bar platesprings are attached onto the fixing stands except the fixing standpositioned substantially at the center of the back electrode substrateso as to fix the back electrode substrate by the elasticity of thepresser bar plate springs.

In the present invention, the distortion caused by the heat to theelectrode unit from other components and impacts or the like from theexterior can be absorbed by contriving the structure of retaining theback electrode substrate with elasticity as described above andpreferably a method of attaching electrode fixing platforms. In otherwords, the present invention can provide a flat-type image displayapparatus with high accuracy and high image quality that can realize andmaintain desired assembly accuracy by absorbing the thermal distortioncaused by the high exposure temperature in fabrication processes andduring operation and is not affected much by vibration/impacts caused byexternal factors.

By maintaining the electrode unit with the pressure of the backelectrode caused by vacuum deformation of the rear case, the influenceon the electrode unit in thermal processes is eliminated, and furtherwhen the electrode unit resonates due to external forces such asvibration, impact from falling, or the like, its amplitude is held down,thus preventing the contact with the linear cathodes.

In addition, screen-like back electrode plates are arranged in parallelto the plurality of linear cathodes. By applying suitable voltage to theback electrode plates, the electric fields in the vicinities of therespective linear cathodes become uniform and the difference inelectron-beam emission capacity among the linear cathodes is cancelled.Thus, uniform images without unevenness in luminance can be obtained.

Moreover, by placing a getter in the space between the rear case and theback electrode substrate whose peripheral portion is bent in a flangeshape, spattered getter is stopped by the back electrode substrate andthe flange portion and therefore does not adhere onto the linearcathodes and the outgoing terminals, thus preventing bad insulation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partially enlarged cross-sectional view showing thestructure of a corner portion in an electrode support device of thepresent invention.

FIG. 2 is an exploded perspective view showing an example of theschematic assembly structure of the electrode support device in aflat-type image display apparatus of the present invention.

FIG. 3 is a schematic plan view of the electrode support device in FIG.2.

FIG. 4 is a schematic perspective view showing the structure in which aback electrode substrate and an electrode unit are fixed in the presentinvention.

FIG. 5 is a cross-sectional view schematically showing a side face ofthe electrode support device according to the present invention.

FIG. 6 is a schematic view showing the state where conductive films havebeen formed on side faces of back electrode plates.

FIG. 7 is an exploded perspective view showing the internal structure ofa flat-type image display apparatus.

FIG. 8 is a perspective view showing the appearance of a flat-type imagedisplay apparatus.

FIG. 9 is a plan view showing an example of the arrangement of electrodesupport plates and electrode fixing plates that are attached to theinner face of a rear case of a conventional flat-type image displaydevice and illustrating the state of thermal expansion/thermaldistortion due to thermal processes schematically.

FIG. 10 is a partially enlarged cross-sectional view schematicallyshowing a schematic electrode-unit mounting structure in which electrodesupport plates and electrode fixing plates that are assembled inparallel-crosses form are fixed to fixing stands in the flat-type imagedisplay apparatus in FIG. 9.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be explained with referenceto the drawings as follows. In the present specification, the same partsare indicated with the same reference characters for easy understandingas long as there is no inconvenience.

FIG. 2 is an exploded perspective view showing an example of theschematic assembly structure of an electrode support device in aflat-type image display apparatus of the present invention. FIG. 3 is aschematic plan view of the electrode support device in FIG. 2.

As shown in FIGS. 2 and 3, a plurality of back electrode plates 34 a-34e are equally spaced in a screen-like manner on a back electrodesubstrate 33 that functions as a back electrode. At predeterminedpositions of four corners, slits 35 a-35 d are formed. On the otherhand, a plurality of metal fixing stands 32 a-32 e that are baked andfixed with low melting point glass are formed on the inner face of arear case 10. The positions of the fixing stands 32 a-32 d except thefixing stand 32 e at the center correspond to the positions of the slits35 a-35 d in the back electrode substrate 33 respectively.

The substrate 33 is mounted on the fixing stands 32 a-32 e on the rearcase 10 as shown in FIG. 3. The fixing stand 32 e at the center and thecentral portion of the substrate 33 are fixed by welding. Presser barplate springs 36 a-36 d for pressing the substrate are fixed to theremaining fixing stands 32 a-32 d by welding. The substrate 33 is fixedwhile being pressed against the fixing stands due to the elasticity ofthe springs with the substrate 33 being sandwiched between the fixingstands and the springs at respective slits in the substrate 33. In FIG.2, the springs 36 b and 36 c were omitted.

More specifically, after the respective springs 36 a-36 d are insertedinto recessed portions of the slits 35 a-35 d at corners of thesubstrate 33 so as to fit therein, the bottom faces of the springs arebrought into contact with the upper faces of the fixing stands 32 a-32 dthat have been fixed to the rear case 10. Then, the springs 36 a-36 dand the upper faces of the fixing stands 32 a-32 d are fixed by welding.

As described above, in the flat-type image display apparatus of thepresent invention, the central portion of the substrate 33 and thefixing stand 32 e are fixed directly by welding, and the slits at thecorners are not fixed to the corresponding fixing stands 32 a-32 ddirectly but the springs 36 a-36 d press and retain the substrate 33,thus fixing respective fixing stands 32 a-32 e and the back electrodesubstrate 33.

FIG. 1 is a cross-sectional view showing the structure of a cornerportion of an electrode support device of the present invention. FIG. 1is a detail view showing electrode supporting structure, particularlythe structure in which a back electrode substrate 33 is pressed andretained by a fixing stand 32 (32 a-32 d) and a presser bar plate spring36 (36 a-36 d) for pressing the substrate.

As shown in FIG. 1, the spring 36 is inserted into a slit 35 in thesubstrate 33, and the spring 36 and the upper face of the fixing stand32 are brought into contact and then are fixed by welding. The spring 36is shown partially in a cross-sectional view.

Further, as shown in FIGS. 1 and 2, a rising bent pawl 37 is provided onthe end face in the outer side in the axial direction of the spring 36so as to form one component with the spring 36. The pawl 37 is widerthan the slit 35 and has a height with some tolerance for the platethickness at the slit portion in the substrate 33. The pawl 37 isdesigned so as to cover the upper face of the substrate 33 with a smallspace 37′ when the spring 36 is inserted into the slit in the substrate33 and is fixed to the fixing stand 32 by welding. This structure isemployed so that the retention with the elasticity by the spring 36takes precedence.

This pawl 37 is not designed for pressing down and fixing the substrate33 but for serving as a pressure pawl for preventing the lift-offdistortion caused by the thermal processes in the fabrication processesof the flat-type image display apparatus according to the presentinvention and the lift-off displacement of the electrode support devicedue to any external factors of vibration, impact, or the like aftercompletion of the apparatus.

It is important that the spring 36 has a size that allows the spring 36to be inserted into and fit inside the slit 35 in the substrate 33 withsufficient allowance both in length and width. This allowance serves forabsorbing metrication error of components and the thermal deformationcaused by the difference in coefficient of thermal expansion among thecomponents.

The quality of the metallic material forming the electrode supportdevice that is assembled in a screen-like manner is also comprehensivelyimportant for solving the problems described in the foregoing section.If possible, it is preferable that the metallic material has comparablethermal characteristics to those of glass forming a front case 9 and therear case 10. In a conventional example, it was difficult to deal withthe complex thermal change caused by the use of dissimilar metals suchas a 36 Ni—Fe alloy used for the electrode plates and a 50 Ni—Fe alloyused for the electrode support plates/electrode fixing plates asdescribed above in addition to the combination of the thick glass platesand the thin metal sheets. On the contrary, in the present invention, inorder to solve the problems in the conventional example, it is preferredto use a material with the same quality as that of the material used forthe electrode plates for both the back electrode substrate 33 and theback electrode plates 34 (34 a-34 e) forming the electrode supportdevice. However, since the difference in thermal expansion due to thedifferent materials can be absorbed by the elasticity of the spring 36fixed to the fixing stand 32 by welding as described above, even iron iswell applicable in considering the costs.

FIG. 4 is a schematic perspective view showing the structure in whichthe back electrode substrate and the electrode unit are fixed. A methodof fixing the electrode unit using electrode fixing platforms will beexplained with reference to FIG. 4.

An electrode fixing platform 41 is positioned at a corner (four corners)of the back electrode substrate 33. A fixed part 42 and a stopper 43 ofthe platform 41 are inserted into a slit 44 for the fixed part and aslit 45 for the stopper respectively that are provided in the substrate33. The flange-shaped bent portion in the substrate 33 and only thefixed portion 42 of the platform 41 are fixed by welding.

The electrode unit 11 is fastened and fixed with a screw 24 for mountingthe electrode unit at a screw hole 46 provided in the platform 41 via aninsulating film 47 placed around the screw hole 46. In this case, theheight of the insulating film 47 placed on the platform 41 is setsuitably to be lower than that of the insulators 40 (see FIGS. 1 and 2)on the upper faces of the back electrode plates 34, so that the lowerface of the electrode unit is pressed against the upper face of theplates 34 when the electrode unit 11 is fastened and fixed (see FIG. 1).Thus, the stress caused by the deformation of the rear case 10 indrawing a vacuum, which will be described later, can be transmitted tothe electrode unit 11, thus improving the accuracy in the superpositiondirection of the electrode unit 11.

Further, the platform 41 is fixed by welding only at the fixed part 42at one end. The stopper 43 at the other end is set to be free. Thus, thedifference in thermal expansion between the substrate 33 and theelectrode unit 11 is absorbed by making use of the flexibility of theplatform 41, and at the same time when impact caused by falling or thelike is applied, the stopper 43 is pressed against the substrate 33,thus preventing the deformation of the electrode unit 11.

In the above, mainly the method for dealing with the displacement in thehorizontal plane parallel to a screen of the flat-type image displayapparatus during the thermal processes was explained. Further, anelectrode support device as a system for solving the problem of verticaldisplacement during the thermal processes will be explained withreference to FIG. 5.

FIG. 5 is a cross-sectional view schematically showing a side face ofthe electrode support device of the present invention. The backelectrode substrate 33 on which the back electrode plates 34 a-34 e areassembled in a screen-like manner is mounted on the upper faces of thefixing stands 32 a-32 e that are positioned on the rear case 10 by beingfixed with low melting point glass. The substrate 33 and the fixingstands are fixed by welding directly and indirectly by the methoddescribed in the above with reference to FIGS. 1 and 2. Further, theelectrode unit 11 is placed on the back electrode plates 34 forming ascreen-like supporting frame, and as described with reference to FIG. 4,the electrode unit 11 and electrode fixing platforms (not shown in thefigure) provided at corners of the substrate 33 are fixed with screws.

In the process of sealing the glass case and drawing a vacuum on itsinside during the thermal process, the rear case 10 is deformed as shownwith an alternate long and short dash line 50 in FIG. 5 due to theattraction pulling the rear case 10 inward. By applying this deformationto the electrode unit positively to increase the pressing force betweenthe electrode unit 11 and the back electrode plates 34, the deformationof the electrode unit 11 due to external forces such as vibration,impact from falling, or the like can be prevented. Further, regardlessof the accuracy in flatness of respective single components in theelectrode unit 11, the assembly accuracy in flatness depends on thevolume of vacuum deformation of the substrate 33 forming the screen-likesupporting frame and the rear case 10. Therefore, the yield of theaccuracy in flatness of respective single components in the electrodeunit 11 can be improved.

When the plurality of back electrode plates 34 are formed to have ashape substantially of an upward convex curve so that their centralportions are higher than their peripheral portions respectively, theaccuracy of the electrode unit is further improved.

As shown in FIG. 8, outgoing terminals 19 leading to the outside fromthe periphery of the glass case are formed before sealing the glasscase. The front case 9 and the rear case 10 of the glass case are sealedand fixed with low melting point glass at the same time whilemaintaining the tension of pulling the electrode unit 11 downward by theterminals 19, thus preventing the electrode unit from being deformed.

Next, the electron-beam emission of the linear cathodes will beexplained with reference to FIG. 1. The linear cathodes 2 are stretchedin parallel to the back electrode plates 34 in the spaces between thescreen-like back electrode plates 34 arranged in parallel. By applying asuitable voltage that is lower than that applied to an electron beamextracting electrode 3 (see FIG. 7) to the plates 34, a uniform spacefield is applied to respective linear cathodes. Therefore, an acuteemission angle of the electron beams emitted from the linear cathodes 2can be obtained, thus increasing the amount of electron beams passingthrough the electron beam extracting electrode 3 and thus improvingluminance.

As shown in FIG. 6, a conductive film (right) 48 and a conductive film(left) 49 are applied to respective left and right back electrode plates34 sandwiching respective linear cathodes 2, respectively. By applyingdifferent voltages to the conductive film (right) 48 and the conductivefilm (left) 49, the variation in emission angle and in amount ofelectron beams emitted that are caused by the variation in accuracy ofthe back electrode plates 34 can be adjusted to be uniform.

Since back electrode plates 34 are placed at the left and right sides ofall the linear cathodes 2, the electric fields around all the linearcathodes 2 become uniform and the amount of electron beams emitted alsobecomes uniform, thus eliminating the unevenness in luminance.

Furthermore, the linear cathodes 2 are surrounded by the back electrodeplates 34, the back electrode substrate 33, and the electron beamextracting electrode 3. Therefore, electron leakage to the outside(especially in the vicinity of the case) does not occur, thus preventinghigh voltage discharge.

As shown in FIG. 1, getter 52 that absorbs gases in a vacuum is placedin the space between the rear case 10 and the back electrode substrate33 provided with a flange-shaped bent portion at its periphery.Therefore, spattered getter is stopped at the bent portion of thesubstrate 33 and therefore does not adhere onto the linear cathodes 2and the outgoing terminals, thus preventing bad insulation.

INDUSTRIAL APPLICABILITY

The present invention realizes a buffer effect for external impacts andthermal distortion in an inplane direction parallel to a screen and in athickness direction by contriving the method of mounting a backelectrode and an electrode unit. Consequently, accuracy, safety, andimage quality of high performance in a flat-type image display apparatuswere secured.

Thus, by making good use of such characteristics, the flat-type imagedisplay apparatus of the present invention can be widely applied as aflat-type image display apparatus used for a television receiver, acomputer-terminal display unit, or the like.

What is claimed is:
 1. A flat-type image display apparatus comprising, in a case formed of a front case and a rear case that is sealed with its inside being in a vacuum condition: a flat-type screen to which phosphors have been applied; a plurality of stretched linear cathodes; an electrode unit including a plurality of sheet-like electrode plates; and a back electrode made of a conductive material; wherein a plurality of fixing stands are attached to an inner face of the rear case, a back electrode substrate that functions as the back electrode is attached onto the fixing stands, the electrode unit is mounted on an upper face of the back electrode substrate, and only one fixing stand positioned substantially at a center of the back electrode substrate in the plurality of fixing stands is fixed to the back electrode substrate, and presser bar plate springs are attached onto the fixing stands except the fixing stand positioned substantially at the center of the back electrode substrate to fix the back electrode substrate by elasticity of the presser bar plate springs.
 2. The flat-type image display apparatus according to claim 1, wherein the back electrode substrate is provided with slits at predetermined positions, the presser bar plate springs are inserted into the slits to bring lower faces of ends of the presser bar plate springs into contact with an upper face of the back electrode substrate, the presser bar plate springs and the fixing stands are fixed so that the presser bar plate springs press the upper face of the back electrode substrate downward.
 3. The flat-type image display apparatus according to claim 1, wherein one or a plurality of bent pawls is formed at an end opposite to a pressing part of each presser bar plate spring to form one component with the presser bar plate spring and thus a function for preventing lift-off of the back electrode substrate is applied to the bent pawls.
 4. The flat-type image display apparatus according to claim 1, wherein a plurality of back electrode plates are attached to the back electrode substrate in a screen-like manner.
 5. The flat-type image display apparatus according to claim 1, wherein electrode fixing platforms are attached to the back electrode substrate at predetermined positions and the electrode unit is fixed to the electrode fixing platforms via insulators.
 6. The flat-type image display apparatus according to claim 5, wherein the electrode unit is fastened and fixed to the electrode fixing platforms with screws.
 7. The flat-type image display apparatus according to claim 5, wherein a plurality of back electrode plates are attached to the back electrode substrate in a screen-like manner and the back electrode plates and the electrode unit are brought into contact with each other via insulators.
 8. The flat-type image display apparatus according to claim 7, wherein a height of upper faces of the insulators on upper faces of the electrode fixing platforms is lower than that of upper faces of the insulators on the back electrode plates.
 9. The flat-type image display apparatus according to claim 7, wherein a central portion is higher than peripheral portions in each back electrode plate.
 10. The flat-type image display apparatus according to claim 7, wherein pressure that is caused in sealing the case with its inside being in a vacuum condition and attempts to deform the rear case can be transmitted to the electrode unit through the fixing stands, the back electrode substrate and the back electrode plates.
 11. The flat-type image display apparatus according to claim 5, wherein the electrode fixing platforms are attached to the back electrode substrate so as to be displaced elastically, one or a plurality of pawls is provided to each electrode fixing platform to form one component, and a function for preventing lift-off of the electrode unit is applied to the pawls.
 12. The flat-type image display apparatus according to claim 4, wherein the plurality of back electrode plates are arranged substantially in parallel and in respective spaces between the back electrode plates, one or a plurality of linear cathodes are stretched substantially in parallel to the back electrode plates.
 13. The flat-type image display apparatus according to claim 12, wherein the plurality of back electrode plates are made of a conductive material and a lower voltage than that applied to an electron beam extracting electrode in the electrode unit is applied to the plurality of back electrode plates.
 14. The flat-type image display apparatus according to claim 12, wherein conductive members are applied onto both faces of each of the plurality of back electrode plates and different voltages are applied to opposed conductive members.
 15. The flat-type image display apparatus according to claim 12, wherein the one or the plurality of linear cathodes is surrounded by the screen-like back electrode plates, the back electrode substrate, and the electrode unit.
 16. The flat-type image display apparatus according to claim 1, wherein periphery of the back electrode substrate is bent toward the rear case in a flange shape, and in a space between the back electrode substrate and the rear case, getter that absorbs gasses in a vacuum is placed. 